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https://issues.apache.org/jira/browse/YARN-11643?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17804587#comment-17804587
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ASF GitHub Bot commented on YARN-11643:
---------------------------------------
laysfire opened a new pull request, #6426:
URL: https://github.com/apache/hadoop/pull/6426
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### Description of PR
JIRA: [YARN-11643](https://issues.apache.org/jira/browse/YARN-11643). Skip
unnecessary pre-check in Multi Node Placement.
Scheduler may do useless while loop when Multi Node Placement enable. This
lead to poor schedule performance in worst-case scenario.
### How was this patch tested?
### For code changes:
- [ ] Does the title or this PR starts with the corresponding JIRA issue id
(e.g. 'HADOOP-17799. Your PR title ...')?
- [ ] Object storage: have the integration tests been executed and the
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- [ ] If adding new dependencies to the code, are these dependencies
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> Skip unnecessary pre-check in Multi Node Placement
> --------------------------------------------------
>
> Key: YARN-11643
> URL: https://issues.apache.org/jira/browse/YARN-11643
> Project: Hadoop YARN
> Issue Type: Improvement
> Components: capacityscheduler
> Reporter: Xie YiFan
> Assignee: Xie YiFan
> Priority: Minor
>
> When Multi Node Placement enabled, RegularContainerAllocator do a while loop
> to find one node from candidate set to allocate for a given scheduler key.
> Before do allocate, pre-check be called to check if current node satisfies
> check. If this node does not pass all checks, just continue to next node.
> {code:java}
> if (reservedContainer == null) {
> result = preCheckForNodeCandidateSet(node,
> schedulingMode, resourceLimits, schedulerKey);
> if (null != result) {
> continue;
> }
> } {code}
> But some checks are related to scheduler Key or Application which return
> PRIORITY_SKIPPED or APP_SKIPPED. It means that if first node does not pass
> check, the following nodes also do not pass.
> If cluster have 5000 nodes in default partition, Scheduler will waste 5000
> times loop for just one scheduler key.
>
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